Methods of making sheet material

ABSTRACT

1. A METHOD OF PRODUCING SHEET MATERIAL HAVING A PREDETERMINED PATTERN OF FILM AREAS INTERCONNECTED BY FIBROUS ARES COMPRISING: LINE POLYMER, SAID FILM COMPRISING A PREDETERMINED PATTERN OF FILMS AREAS AND A REMAINDER PORTION, SAID PREDETERMINED PATTERN OF FILM AREAS BEING LESS CAPABLE, AFTER STRETCHING OF SAID FILM IN A DIRECTION, OF BEING SPLIT INTO FIBERS THAN SAID REMAINDER PORTION, STRETCHING THE FILM IN A DIRECTION TO AN EXTENT WHEREBY SAID REMAINDER PORTION IS CAPABLE OF BEING SPLIT INTO FIBERS, AND TREATING AREAS COMPRISING A SAID REMAINDER PORTION INTO FIBERS AREAS COMPRISING A MULTIPLICITY OF FINE FIBERS UNIFORMLY DISTRIBUTED THROUGHOUT SAID FIBROUS AREAS, SAID FIBROUS AREAS INTERCONNECTING SAID FILM AREAS.

Nov. 26, 1974 c. HARMON ETTAL 3,851,034

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1974 c. HARMON ETAL 3.351.034

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METHODS OF MAKING SHEE'I' IATERIAL Original Filed Nov. 1'7, 1966 '7Sheets-Sheet Nov. 26, 1974 c. HARMON ETAL HETHODS 0F UAKING SHEETMATERIAL 7 Sheets-Sheet Original Filed NOV. 17, 1966 MJLM Q 1974 cHARMON ETAL 3,351,034

HETHODS 0F BAKING SHEET HATERIAL Qriginal Filed Nov. 17, 1.966 7Sheets-Sheet '7 United States Patent 3,851,034 METHODS OF MAKING SHEETMATERIAL Carlyle Harmon, Scotch Plains, N.J., and William Sibbach,Longmeadow, Mass, assignors to Johnson & Johnson Application July 7,1970, Ser. No. 52,989, now Patent 3,746,607, which is acontinuation-in-part of abandoned application Ser. No. 595,152, Nov. 17,1966. Divided and this application Sept. 20, 1972, Ser. No. 290,671

Int. Cl. 132% 7/18 U.S. Cl. 264-147 9 Claims ABSTRACT OF THE DISCLOSUREA tear resistant sheet material having a soft, fibrous hand. The sheetmaterial has a predetermined pattern of film areas of crystalline,orientable polymer. These film areas are interconnected by fibrous areasof substantially the same polymer and these film areas are substantiallythicker than the fibrous areas. The fibrous areas have a multiplicity offine fibers uniformly distributed throughout the area. A process forproducing said sheet mateterials, comprising: producing a film in whichthere are patterned areas having different orientation properties;stretching the film to orient the film in a pattern of areas; andfibrillating or splitting the film in a pattern.

This is a division of our co-pending application Ser. No. 52,989, filedJuly 7, 1970, now US. 3,746,607, which in turn is a continuation-in-partof application Ser. No. 595,152, filed Nov. 17, 1966, now abandoned.

This invention relates to new sheet material, and more particularly, tosheet material combining plastic film and fibers into a unitary materialand to methods for manufacturing such sheet material.

BACKGROUND OF INVENTION For some time, plastic films have been producedwith various patterns. Recently, methods have been developed forproducing film materials having a pattern of hubs or bosses of filmconnected by biaxially oriented areas to form a pattern. These orientedareas for the most part are thick, rod like sections and in someinstances, may be considered monofilaments. These products, while havinga pleasing appearance, are still plastic in nature and lack a soft handand have relatively poor drape.

Another recent technique for changing the properties of a plastic filmis to highly orient the film, uniaxially, and then split the film intofine fibers. While this technique may provide suitable softness and handin the product, its strength transverse to the direction of orientationis very poor and the material will readily tear in the direction oforientation.

The sheet material of the present invention overcomes many of theabove-mentioned shortcomings. Our new product has a soft hand whilehaving strength and tear resistance in both the longitudinal andtransverse directions or other directions of the product.

SUMMARY OF THE INVENTION The sheet material of the present inventioncomprises a plurality of areas of plastic film arranged in apredetermined pattern. The plastic film areas may be oriented orunoriented or a combination of oriented and unoriented plastic film.Adjacent areas of plastic film are connected by a plurality of fibrousareas to form a unitary sheet material. The fibrous areas lie in thesame general plane as the plastic film areas.

The plastic film areas are distributed throughout the sheet material ina predetermined pattern. The size of the areas may vary over a widerange, and it is preferred 3,851,034 Patented Nov. 26, 1974 that if thefilm areas are unoriented, the pattern be intermittent, that is, anunoriented area does not extend entirely across the width of the web orentirely along the length of the web. If the plastic film area isoriented, it may be desirable to have the oriented areas extend fullyalong the length of the web or fully across the width of the web toprovide great strength in the final sheet material. The film areas maytake various shapes, such as, circles, squares, hexagonals, rectangles,or other multi sided figures. The size, shape, and distribution of theplastic film areas will determine to a great extent the method by whichthe sheet material of the present in vention may be produced as will bemore fully described hereinafter.

The film areas are connected by fibrous areas and depending upon thepattern of film areas, the film areas may be connected to allsurrounding film areas or only to specific adjacent film areas. Thefibrous areas comprise a plurality of small fibers extending from onefilm area to another film area. These fibrous areas contain amultiplicity of fine fibers substantially uniformly distributedthroughout the area. The individual fibers in the area have a denier ofless than 10 and preferably have a denier of about 1 or lower. Thefibrous areas lie in the same plane as the film areas. The film areasare thicker than the individual fibers though because of the fluffinessof the fine fibers, the fibrous areas may have substantial apparentthickness. If the film areas are unoriented, they may be substantiallythicker than the fibrous areas.

The length of the fibers will depend upon the distance between filmareas and a fiber may cover this full length or it may be somewhatshorter than this distance. Generally, fibers will be of substantiallythe same polymeric composition as the film areas though in certainmethods of the present invention, there may be slight modifications inthe polymeric compositions of the film areas and the fibrous areas.

In one modification of the sheet material of the present invention,unoriented film areas may be connected by oriented film areas and alsobe connected by fibrous areas. The oriented areas may be eitheruniaxially oriented or biaxially oriented, again dependent on the methodfor manufacturing the sheet material of the present invention.

As the present description progresses, it will become apparent thatthere are innumerable variations, permutations, and computations oforiented plastic film areas and/ or unoriented plastic film areas andfibrous areas which may be combined to produce sheet material accordingto the present invention.

In manufacturing the sheet materials of the present invention, a plasticfilm is treated to provide the film with a predetermined pattern ofareas which will resist orientation to a greater extent than theremainder of the film. Stretching forces are applied to the film in oneor more directions. The force applied is of a magnitude such as willhighly orient portions of the film but not of sufficient magnitude tofully orient those areas of the film treated to resist orientation. Thepatterned oriented film is then fibrillated or treated to split thehighly oriented sections into individual fibers. This treatment may begiven to the entire area, or it may be given to the film in a pattern sothat only certain highly oriented areas are fibrillated or split intofibers as will be more fully described hereinafter.

The oriented area to be fibrillated must be oriented sufiiciently to bebrittle. If an unmodified polypropylene material is used, it should beoriented at a ratio of 9 to 10 to 1 or higher in order to befibrillatable. This stretch ratio may be reduced somewhat by modifyingthe polypropylene by foaming or adding material to increase itsbrittleness. It is believed that the highly oriented material isfibrillatable because of the ratio of crystalline to amorphous portions.By reducing the amorphous portions, the crystalline portion is not heldtogether sufiiciently and hence, is readily fibrillatable. Anothertechnique to produce fibrillatable areas is to make the area thin enoughso that many fine crystals are formed in the area and the ratio ofcrystalline to amorphous portions is increased.

If desired, a film may be treated a number of times to give the filmvarious areas having different degrees of resistance to orientation sothat when stretched and fibrillated, there remain unoriented areas andalso oriented areas which have not been oriented to the extent, wherein,they are capable of being split into fibers or fibrillated. The forcesto produce orientation may be applied to the film in one or moredirections and the forces to fibrillate or split the film may also beapplied in one or more directions.

. The sheet material of the present invention may be made from any ofthe plastic materials which readily form films and are orientable to thedegree that they readily form fibers. These plastic materials have ahigh molecular weight, a long chain molecular structure and arecrystalline. Suitable examples are the polyolefins, such as polyethyleneand polypropylene or copoylmers thereof, polyamides, polyesters, etc.The type of polymer used will have considerable influence on the methodsused in producing the sheet material of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fullydescribed in conjunction with the accompanying drawings, wherein:

FIG. 1 is a plan of a suitable starting material from which a product ofthe present invention may be produced;

FIG. 2 is a cross sectional view taken along line 22 of FIG. 1;

FIG. 3 is the starting material of FIG. 1 after it has been treated bystretching in the transverse direction;

FIG. 4 is a plan view of the material of FIG. 3 after splitting forceshave been applied to the material in the longitudinal direction;

FIG. 5 is a cross sectional view taken along line 55 of FIG. 4;

FIG. 6 is a plan view of another type of starting material from whichproducts of the present invention may be produced;

FIG. 7 is a cross sectional view taken along line 7-7 of FIG. 6;

FIG. 8 is a plan view of the material of FIG. 6 after it has beenstretched in the transverse direction;

FIG. 9 is a plan view of the material of FIG. 8 after that material hashad splitting forces applied and been stretched in the longitudinaldirection;

FIG. 10 is still another type of starting material from which productsof the present invention may be produced;

FIG. 11 is a cross sectional view taken along line 1111 of FIG. 10;

FIG. 12 is a plan view of a product according to the present inventionproduced in accordance with the methods of the present invention;

FIG. 13 is a plan view of another product of the prodnot of the presentinvention;

FIG. 14 is a plan view of another embodiment of the product of thepresent invention;

FIG. 15 is a plan view of a product of the present invention;

FIG. 16 is a plan view of the product of the present invention;

FIG. 17 is a schematic flow sheet of the process of the presentinvention showing the various steps in the process;

FIG. 18 is a schematic drawing of suitable apparatus for carrying outone embodiment of the process of the present invention; and

FIG. 19 is a schematic drawing of apparatus for carrying out anotherembodiment of the process of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to the drawings, FIGS. 1and 2, there is shown a plastic film 30 which may be oriented uponstretching. The film is cast with thin areas 31 and thick areas 32 inthe film with the thicker areas being narrow longitudinal ribs. The filmis preferably heated to below the melting point of the polymer and isstretched in a transverse direction (arrow A) to produce the film 33depicted in FIG. 3. The thicker narrow longitudinal ribs 32 remainunoriented, whereas, the wider thin channels 31 have become oriented inthe transverse direction.

As shown in FIGS. 4 and 5 repeated intermittent forces have been appliedin the lingitudinal direction (arrow B) of the film 33 to break, crackand fibrillate the oriented areas 31 and produce fibers or split fibers35 without affecting the unoriented thick ribs 32. The unoriented areasare connected to adjacent unoriented areas by fibers which extendbetween areas. There are also considerable fibers which do not extendthe full distance between areas but only partially cover the distance toproduce a fiutfy and bulkiness between areas.

Referring to FIGS. 6 and 7 there is shown another plastic film 37capable of being oriented when stretched which is cast in a differentpattern and which may be used to produce the products of the presentinvention. The film comprises thin square areas 38 and thickertransverse ribs 39 and longitudinal ribs 40 with square areas 41 at eachof the intersections of these ribs. In FIG. 8, the film of FIG. 6 hasbeen stretched in the transverse direction (arrow C) to highly orientthe thin areas 38 and orient the thick transverse ribs 39 with noorientation in the longitudinal ribs 40 and with little orientation atthe intersection. The film is treated with longitudinal splitting forcesto split the highly oriented areas. The thin areas 38 are split intofine fibers 42, whereas, the thick transverse ribs 39, if split, formcoarser fibers. The film is heated slightly and stretched in thelongitudinal direction (see arrow D, FIG. 9) to orient the thicklongitudinal ribs 40, further orient the intersections 41, and open thefibrous areas 44 to produce the fabric 43 as shown in FIG. 9. The fabriccomprises substantially oriented transverse ribs of coarse fibers 39,longitudinal oriented ribs 40 and partially oriented areas 41 where thetransverse and longitudinal ribs intersect, with panes of open fibrousareas 44 connecting the film areas.

Referring to FIGS. 10 and 11, there is shown yet another plastic film 47which may be used in accordance with the present invention to producethe products of this invention. In this film there are thick areas ofdots 48 arranged in transverse and longitudinal rows. Connecting thesedots in both the transverse and longitudinal direction are thinner ribs49. In the area defined by these ribs and dots is yet a thinner plasticfilm 50. When this film 47 is stretched both in the cross and longdirection and fibrillated in accordance with the present invention, afabric 51 as depicted in FIG. 12 is produced. The fabric comprises dotsof unoriented plastic film 48 arranged transverse and longitudinal ofthe fabric. These dots are connected by ribs of oriented film 52 runningboth in the longitudinal direction and in the transverse direction. Theribs are substantially oriented in the major dimension of the rib, andin some instances may be made of coarse fibers. The ribs define fibrousareas 53.

Referring to FIG. 13 there is shown sheet material 55 of the presentinvention comprising thick ribs 56 running transversely of the sheetmaterial which are unoriented film. There are thick ribs 57 connectingthe transverse lines which are substantially uniaxially oriented or maycomprise coarse fibers and within the ribs are fibrous areas 58. In FIG.14 there is shown still another embodiment of the product of the presentinvention in which there are biaxially oriented thick film ribs 62extending diagonally across the fabric in opposite directions with thearea 63 defined by these ribs being fibrous in nature.

Sheet material as shown in FIG. 13 may be produced from a suitable filmembossed or cast to produce thicker transverse and longitudinal lines.The film is stretched in the longitudinal direction to orient the thinarea longitudinally and also orient the thicker longitudinal ribs. Whensplitting forces are applied to this film, the oriented areas formcoarse fibers in the thick areas and fine fibers in the thin areas toproduce the rfinal product.

With regard to FIG. 14, the product as depicted may be produced from afilm in which the diagonal ribs are thicker than the area surrounded bythe ribs. The film is stretched lengthwise, fibrillated, and stretchedin the transverse direction to produce the product described inaccordance with FIG. 14.

In FIG. 15, there is shown a product 65 of the present invention inwhich there are transverse lines 66 of highly oriented film which areconnected by very open fiber areas 67. This fabric may be produced froma film embossed or cast to produce thicker transverse lines and which isstretched longitudinally to orient the thinner areas between the thicklines in the longitudinal direction. Fibrillating or splitting forcesare applied in a transverse direction to form the highly oriented thinareas into fibers. The film is stretched in the transverse directionwhich orients the thicker lines and opens the fibrous areas to producethe product described in accordance with FIG. 15.

Referring to FIG. 16, there is shown yet another embodiment of thepresent invention comprising circular areas 68 of unoriented filmarranged in staggered rows and connected to adjacent circular areas byfibrous areas 69 to form a unitary fabric. This product may be producedby orienting a tfilm of uniform thickness, longitudinally to a highdegree of orientation, applying heat in the pattern of the circularareas to reduce the orientation of these areas and then submitting thefilm to transverse fibrillating or splitting forces to change theoriented areas into fibrous areas to produce the product described inaccordance with FIG. 16.

The polymers which may be used to produce the sheet materials of thepresent invention may be any of the orientable, crystalline film formingpolymers. These are usually synthetic, organic polymers of highmolecular weight with long chain molecules and are thermoplastic innature. Suitable examples of such polymers are the polyolefins, such as,polyethylene and polypropylene, the polyamides, the polyurethanes, thepolyesters and polyethers, copolymers of these various long chainpolymers or mixtures of these polymers including mixtures ofnoncompatible polymers and mixtures with foreign substances such asclay, sand, etc. which may be added to aid in the splitting operation.The important thing is that the polymer must be film-forming and musthave a capacity, wherein, the molecules are capable of being orientedupon proper treatment. This orientation is important in order to producefibrous areas in the new types of sheet material of the presentinvention.

In all instances the sheet materials of the present in vention willcontain fibrous areas, that is, areas where the polymer is in thefiber-form. The fibers in the sheet material are of a rectangular crosssection and of a random denier ranging anywhere from tenths of a denierup to denier. The fibrous areas may be quite open and in some instances,the sheet material may even have holes depending upon the degree oforientation, fibrillation and stretching given the sheet material andwhether such stretching is carried out before or after fibrillation.

' In all instances in the sheet materials of the present invention, thefibrous areas will be connected by either unoriented areas or orientedareas of the synthetic polymer to form a unitary fabric. These syntheticpolymer areas may be either completely unoriented or have varyingdegrees of either uniaxial or biaxial orientation up 6 to a very highlyoriented form. It is extremely important that there be such unorientedor oriented areas in order to stop the formation of fibers and preventthe sheet material from splitting either along its entire length or itsentire width.

The various patterns which may be used of oriented and/or unorientedareas as compared to fibrous areas may vary widely. They may betransverse or longitudinal lines, dots, rectangles, squares, or variouscombinations of the same. The important thing is that if the fibers arerunning longitudinally, there must be either oriented or unoriented filmareas running transverse of the sheet material to prevent splitting ofthe material in the longitudinal direction, and if the fibers areoriented in the transverse direction, there must be unoriented ororiented areas running longitudinal of the fabric to prevent the sheetmaterial from splitting in the transverse direction. If the oriented andunoriented areas are not continuous, then they should be in a staggeredover-lapping pattern as in FIG. 16 to help prevent splitting.

The properties of the products of the present invention may vary overwide limits dependent upon the combination of oriented, unoriented andfibrous areas used. The fibrous areas, of course, produce porosity inthe sheet materials along with producing the soft, fluffy hand occurringwith fibers. The fibers also being highly oriented will impart strengthto the film in the direction of their orientation. If the sheet materialwas entirely fibrous, it would be readily susceptible to tearingperpendicular to the direction of the orientation of fibers. Theoriented areas have high tear resistance perpendicular to the directionof orientation and hence, provide the sheet material with stop areas toprevent the fibrous areas from splitting or tearing the entire length orwidth of the fabric. The oriented areas also provide strength in thefinal ftbric in the direction of their orientation. The unoriented areasalso provide the stop area or area which prevents tearing.

The sheet materials of the present invention have various uses and maybe used many places where woven or nonwoven fabrics are presently used.The sheet materials may be used as the wrapping for absorbent media,such as in a sanitary napkin or surgical dressing. In such a use, thefibrous area being porous allows material to be absorbed by theabsorbent mass. As most of the linear polymers do not adhere to a woundwhen the material of the present invention is used as a covering for adressing, the resultant dressing is nonadherent. The sheet materials ofthe present invention, being inert and highly resistant to weathering,may be used as seed bed covers or for other outdoor uses. When athermoplastic polymer is used in the formation of the sheet material,the resultant product could be used as an adhesive member for thelamination of fabrics, etc. They may also be used a packaging materials,backing for carpeting, decorative purposes, such as curtains and drapes,apparel, etc.

The general process for producing the products of the present inventioncomprises three basic steps as follows: 1) producing a film in whichthere are patterned areas having different stretch or orientationproperties, (2) stretching the film to orient the film in a pattern ofareas, and (3) fibrillating or splitting the film in a pattern. Thesethree basic steps may be combined in various manners and sequence andone or more of the steps may be repeated one or more times. The variouscombinations of the process of the present invention may be more clearlyunderstood when taken in conjunction with the flow sheet depicted inFIG. 17. In the process of the present invention, the starting materialis a suitable film-forming polymer (Box 1) as previously described.Initially, a film is formed, and the film may be of two thicknesses (Box2), three or more different thicknesses (Box 3), or it may be of auniform thickness (Box 4). The thicker areas are formed in a pattern aspreviously described, and the film may be formed by casting on anembossed roll or if a uniform film is desired, by a tubular blown filmextrusion or any of the various known methods of forming plastic films.

If a film of uniform thickness (Box 4) is used, it may be treated toproduce areas which have different stretch properties (Box 5). This maybe done by printing the film in a pattern with a cross-linking materialand then curing the cross-linking material so that cross-linked polymerareas are formed which cannot be oriented. Another technique fortreating the film is to place a dark compound, such as, black paint, onthe film in various areas so that the film when heated prior to beingstretched absorbs more heat in certain areas than in other areas, andhence, only the more heat-absorbing areas will become oriented. It isimportant that the film have a pattern of differential stretch which maybe formed either by a physical process, such as embossing, heating,etc., or by a chemical process, such as cross-linking, etc.

The treated film (Box 5) or the film of varying thickness (Boxes 2 and3) is stretched either in the transverse (Box 6) or longitudinaldirections (Box '7) to orient those areas most susceptible toorientation. The other areas may remain completely unoriented or may bepartially oriented. Depending upon the pattern of highly oriented areasproduced in the film, the film may be either split (Box 8 or 13), thatis, treated with forces transverse to the direction of orientation tosplit the highly oriented areas into fibrous areas, or it may beoriented in the opposite direction of its first orientation (Box 9 or14) to orient other areas of the film in a direction 90 degrees to thefirst direction of orientation and then split (Boxes 11 and 16). It isimportant that the splitting forces be applied transverse to the lastdirection of orientation, that is, if the film is stretched in alongitudinal direction, the splitting forces must be applied in thetransverse direction.

Virtually any combination of one or more orientation steps (Boxes 6 and10 or 7 and 11) and one or more splitting steps (Boxes 8 and 12 or 13and 17) may be used. The only limit is that there should not be moresplitting or fibrillating steps than there are orientation steps;however, there may be more orientation steps than there are fibrillatingsteps. As shown in FIG. 17, one stretching step (Box 6) may be combinedwith one splitting step (Box 8) or two stretching steps (Boxes 6 and 9)may be followed by a splitting step (Box 11). If desired, stretchingsteps (Boxes 6 and 10) may be alternated with splitting steps (Boxes 8and 12). In thOse instances when you have a stretching step (Box 10 orafter a splitting step (Box 8 or 13), the stretching step will be in thesame direction as the splitting forces have been applied, and hence,will open up the fibrous area and produce a more porous product. If onlyone stretching step is used in the process of the present invention, theoriented areas will be uniaxially oriented; however, if two stretchingsteps are used, there may be areas in the final product, dependent uponpatterns used, which are biaxially oriented.

Generally, it is preferred to heat the film prior to orientation. Whenheating an unoriented film prior to stretching, temperatures of fromabout 150 F. and higher may be used depending on the polymer beingprocessed, the amount of stretching, rate of stretching, etc. If heatinga film already oriented in one direction, care must be taken not to usetemperatures which will soften the polymer and reduce or destroy thealready desired orientation.

In starting with films of uniform thickness (Box 4), the films may beoriented in a single direction first (Box 18 or 19), and treated in apattern to reduce the orientation in that pattern (Box 20) so that whenthe splitting forces are applied (Box 21 or 2.2), the only areasaffected in the film will be the highly oriented areas. The unorientedareas will be unaffected and remain in the final prod not. As previouslydescribed, such a treated film after being split into fibers may bestretched perpendicular to its original direction of orientation (Box 23or 24) to open up the fibrous areas and produce a more porous product.

liteferring to FIG. 18, there is a schematic showing of apparatus forcarrying out one embodiment of the process of the present invention. Thesuitable film-forming polymer is fed into the hopper 75 of a screwextruder 76 and the plastic film 77 extruded through the slit extrusionopening onto a patterned casting roll 78. The pattern roll is kept coolby internal cooling with chilled water and the film as cast is pressedby the pressure roll 80. The pattern on the casting roll is in theconfiguration as shown in FIG. 6 of the drawings. The film after beingcast is passed about a series of long stretchin rolls with the uppermostrolls 82 and 81 rotating at a slower speed than the lower rolls 83 and84 so that the film is stretched in the longitudinal direction to highlyorient the thin areas of the film and give a substantial orientation tothe thicker longitudinal ribs of the film. The orientation in the thinareas may be 4:1, 10:1 or even as high as 15:1, but it must produce ahighly uniaxially oriented area. The film is brushed with a wire brush85 which in effect is applying forces transverse to the highly orientedareas of the'film breaking these areas into fibers or what is commonlytermed fibrillating these areas. The film is passed through a crossstretching apparatus 86 which is a tenter frame comprising divergingchains which grip the film at its outer edges and spread it widthwise.This widthwise spreading provides a substantial orientation in thetransverse ribs. The areas defined by these oriented areas are fibrousareas. The sheet material is wound on a standard wide up rig 88 as knownin the art.

Referring to FIG. 19, there is also schematically shown other apparatusfor carrying out another embodiment of the process of the presentinvention. In this embodiment a roll of uniform film 90 formed by any ofthe various known forming techniques is first transversely stretching bypassing it through a tenter frame 91 comprising diverging chainconveyors which grip the edge of the film and stretch it transversely toa degree of orientation of from about 6 to 1 to 15 to 1 or higher. It ispreferred that the film be heated prior to being stretched. Thestretched film is passed between a pair of rolls 92 and 93, one of whichhas raised areas 94 which have been heated and which disrupt theorientation in those areas of the film which contact the raised heatedareas. The film is passed between rubber belts 95 with the rubber beltsplaced under high compression which applies longitudinal forces to thefilm and splits those areas which remain highly oriented in thetransverse direction into fibrous areas. The film is passed through aset of stretching rolls which comprise four rolls, the first two rolls96 and 97 running at a slower speed than the latter two rolls 98 and 99to stretch the film in the longitudinal direction to open up the fibrousareas and produce some orientation in the previously unoriented areas.The fabric is then wound up 100 for use as described.

The following are examples of sheet materials and methods according tothis invention. It should be under-' stood that they are offered only byway of illustration and not intended to define the breadth of theinvention or limit the scope of the claims.

EXAMPLE I A linear, high-density polyethylene polymer is extrudedthrough a die and cast onto a pattern casting roll. The pattern on thecasting roll comprises longitudinal and transverse lines spaced /s inchapart in both directions and having a depth of 7 mils. The film producedis a film of 3 mil thickness with transverse and longitudinal linesspaced inch apart in both directions, 10 mils in thickness and 7 mils inwidth. The film is heated to 250 F. and stretched in its longitudinaldirection at a 9:1 ratio to highly orient the thin areas and orient thethicker longitudinal ribs. The film is passed through a fibrillatingapparatus comprising a rotating brush to split the highly oriented areasinto fibrous areas. The partially split'film is again heated to 250 F.and passed through a 'tenter frame to cross stretch the film in a ratioof 6:1 to partially orient the transverse ribs and produce sheetmaterial as described in accordance with the present invention.

EXAMPLE II A linear polyethylene polymer is extruded and cast onto apattern casting roll. The engraved pattern on the casting roll compriseslongitudinal lines spaced 0.1 inch apart. The lines have a depth of 7mils and are mils wide on the face of the roll and 7 mils wide at thebottom of the engraving. The film produced is 3 mils thick with 10 milthick longitudinal ribs. The film is heated to approximately 230 F. andstretched in its transverse direction at an 8 to 1 ratio to orient thethin areas between ribs. Longitudinal forces are applied to split theoriented areas into fibers. The film is heated to approximately 200 F.and stretched in the longitudinal direction at a 2 to 1 ratio topartially orient the thicker longitudinal ribs and open the fibrousareas to produce a sheet material having partially oriented longitudinalribs connected by fibrous areas with the fibers being substantiallyoriented in the transverse direction of the sheet material.

EXAMPLE III A polypropylene polymer is extruded and cast onto a patterncasting roll. The pattern on the casting roll comprises two sets ofengraved diagonal lines which cross each other at about 90. The engravedlines are spaced A; inch apart and are 30 mils wide and 10 mils deep.The film produced is 3 mils thick having a crossing diagonal pattern ofthicker ribs. The film is heated to 300 F. and stretched in itslongitudinal direction at a ratio of 10 to 1 to orient the thin areas.Splitting forces are applied in the transverse direction to form fibersin the thin areas. The film is stretched in the transverse direction ata ratio of 10 to 1. The resultant product is similar to the productdepicted and described in conjunction with FIG. 14.

Having now described the invention in specific detail and exemplifiedthe manner in which it may be carried into practice, it will be readilyapparent to those skilled in the art that innumerable variations,applications, modifications and extensions of the basic principlesinvolved may be made without departing from its scope. Thus, the sheetmaterial of the present invention may be laminated with fabrics, paper,other materials or employed in a host of ways that will be readilyapparent to one skilled in the art.

What is claimed is:

1. A method of producing sheet material having a predetermined patternof film areas interconnected by fibrous areas comprising: forming a filmof an orientable, crystalline polymer, said film comprising apredetermined pattern of film areas and a remainder portion, saidpredetermined pattern of film areas being less capable, after stretchingof said film in a direction, of being split into fibers than saidremainder portion, stretching the film in a direction to an extentwhereby said remainder portion is capable of being split into fibers,and treating the film to fibrillate said remainder portion into fibrousareas comprising a multiplicity of fine fibers uniformly distributedthroughout said fibrous areas, said fibrous areas interconnecting saidfilm areas.

2. A method according to Claim 1, wherein stretching forces are appliedin the longitudinal direction of the film and the film is treated in thetransverse direction to form the oriented areas into fibrous areas.

3. A method according to Claim 1, wherein stretching forces are appliedin the transverse direction of the film and the film is treated in thelongitudinal direction to form the oriented areas into fibrous areas.

4. A method according to Claim 2, wherein stretching forces are appliedto the treated film in the transverse direction to open the fibrousareas and further orient some film areas.

5. A method according to Claim 3, wherein stretching forces are appliedto the treated film in the longitudinal direction to open the fibrousareas and further orient some film areas.

6. Method according to Claim 1, wherein, a film of an orientable,crystalline polymer is formed having thin areas which are readilyorientable and a pattern of thick areas which resist orientation.

7. Method according to Claim 1, wherein a film of an orientable,crystalline polymer is formed having a uniform thickness and is treatedin a predetermined pattern to produce film areas having differentorientation properties than the remainder of the film.

8. The method of Claim 1 wherein said orientable, crystalline polymer ispolypropylene and said film is stretched at a ratio of about 9: 1.

9. The method of Claim 1 wherein said orientable, crystalline polymer ispolyethylene and said film is stretched at a ratio of about 8: 1.

References Cited UNITED STATES PATENTS 3,137,746 6/ 1964 Seymour et a1.264-454 3,164,948 1/1965 Stratford 5714O 3,273,771 9/1966 Beaumont 22533,397,825 8/1968 Wilkins 225-3 3,441,638 4/1969 Patchell et al. 2641543,470,594 10/1969 Kim 28-72 3,485,705 12/1969 Harmon 264Dig. 473,488,415 1/1970 Patchell et all 264-154 3,515,778 6/1970 Fields et al264-147 3,517,098 6/1970 Rasmussen 264-Dig. 47

JAY H. WOO, Primary Examiner US. Cl. X.R.

28-Dig. 1; 264-154, 289, Dig. 47

1. A METHOD OF PRODUCING SHEET MATERIAL HAVING A PREDETERMINED PATTERNOF FILM AREAS INTERCONNECTED BY FIBROUS ARES COMPRISING: LINE POLYMER,SAID FILM COMPRISING A PREDETERMINED PATTERN OF FILMS AREAS AND AREMAINDER PORTION, SAID PREDETERMINED PATTERN OF FILM AREAS BEING LESSCAPABLE, AFTER STRETCHING OF SAID FILM IN A DIRECTION, OF BEING SPLITINTO FIBERS THAN SAID REMAINDER PORTION, STRETCHING THE FILM IN ADIRECTION TO AN EXTENT WHEREBY SAID REMAINDER PORTION IS CAPABLE OFBEING SPLIT INTO FIBERS, AND TREATING AREAS COMPRISING A SAID REMAINDERPORTION INTO FIBERS AREAS COMPRISING A MULTIPLICITY OF FINE FIBERSUNIFORMLY DISTRIBUTED THROUGHOUT SAID FIBROUS AREAS, SAID FIBROUS AREASINTERCONNECTING SAID FILM AREAS.